The present invention relates to an apparatus for drilling into bone, and in one particular aspect to such an apparatus which self centers about an aperture through a work piece.
It is known in the art to apply fasteners for attaching sutures, bone plates, and connective tissue. The fastener is inserted into a hole in a bone and generally through some application of force is caused to expand. One particular method for driving a fastener is disclosed in U.S. Pat. No. 5,398,861 by Green which discloses a spring loaded retractable piston and a pivotable trigger device for releasing the piston and allowing it to drive forward and drive home a fastener. The fasteners are received through holes in a bone plate into holes in the skull. It would be desirable to have a drill for drilling the skull which self centers through the holes in the bone plate.
A self-centering bone drill according to the present invention comprises a drill bit having a proximal end and a distal end, a cutting surface at the distal end, and a first radially extending flange. A tubular housing coaxially receives the drill bit and a spring is coaxially received within the housing, and coaxially receives the drill bit. The spring is compressed between the first radially extending flange and an interior abutment surface on the housing distal of the first radially extending flange to urge the housing distally along the drill bit. A chamfered surface on a distal end of the housing engages a chamfered surface on a workpiece to center the drill bit.
Preferably, the housing comprises a second abutment proximal of the first radially extending flange to inhibit proximal movement of the drill bit out of the housing. It can also comprise a second annular flange, proximal of the first annular flange and an exterior abutment surface exterior of the housing such that abutment of the second annular flange against the exterior abutment surface limits distal movement of the drill bit out of the housing to thereby control the depth of a hole drilled thereby. Preferably, the housing comprises a two-piece collar assembled over the drill bit between the first annular flange and the second annular flange and received coaxially into the housing, the exterior abutment surface being on the collar.
Preferably, the housing has a first bore of a diameter to slidably receive the first annular flange of the drill bit and a second smaller diameter bore to slidably receive the drill bit distal end and the abutment surface comprises an annular surface formed at the transition between the first bore and the second bore.